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Magnetoplasma drive could make Mars transit take 39 days?

orbitalindex.com

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Re: Magnetoplasma drive could make Mars transit take 39 days?

#11

Post by a_crc »

api wrote: post #4
blakesterz wrote: post #2

"A massively scaled up version running at 200 MW could make the one-way transit to Mars in as little as 39 days, but generation of this amount of in-space energy isn’t currently anywhere near possible and would require both an advanced onboard nuclear reactor as well as super-efficient heat radiators. " 200 MW is a helluvalotta power! Disappointing to see it's so far off.

How much thin film PV is that? There's no wind and the solar constant is a lot higher in space even further from the sun. Also remember that space is not dark. Unless you are behind something you are always in daylight if you are near a star.

It's a lot of solar panel. A quick search gives us a figure of 220 watts of power per square meter of space based solar panel. This would mean a 200MW solar collector would need to be almost a million square meters in size. For reference that would be a square the length of 155 NYC city blocks on each side.

Re: Magnetoplasma drive could make Mars transit take 39 days?

#12

Post by elihu »

> The most recent tests of VASIMR have run at 200 kW and expelled ions at 180,000 km/h

Is this the power consumed by the device, or a measurement of the propulsion power created? It would be interesting to know the energy efficiency; i.e. what percentage of the input power is converted to thrust.

Re: Magnetoplasma drive could make Mars transit take 39 days?

#13

Post by d_silin »

elihu wrote: post #12

> The most recent tests of VASIMR have run at 200 kW and expelled ions at 180,000 km/h Is this the power consumed by the device, or a measurement of the propulsion power created? It would be interesting to know the energy efficiency; i.e. what percentage of the input power is converted to thrust.

At least 60%.

Re: Magnetoplasma drive could make Mars transit take 39 days?

#14

Post by UnpossibleJim »

marta_morena_25 wrote: post #6
avmich wrote: post #5

Earlier quoted context omitted.

If we're talking of this kind of efforts, why not to discuss this - https://toughsf.blogspot.com/2019/10/the-expanses-epstein-dr... . Seems in the realm of physics, with some more impressing results...

Yeah this sounds cool. Essentially you could design a large spacecraft and put a fusion reactor in it (we will have viable, positive yield reactors soonish). It should be possible then to power a fusion drive as well by building a sort of "half-open" fusion reactor chamber into which we dispense some of the plasma without any pressurization. It should essentially cause a massive explosion, that if somehow controlled…

To my understanding of physics, there is almost no amount of thrust that would actually propel us to the speed of light, in reality. The energy costs alone would simply be too enormous.

"Folding space"/"Warping space", or shrinking the space in front of the craft while expanding the space, would seem to be the only theoretical way to achieve speeds that not only would match light speed but could surpass it and not break the laws of physics as we understand them. The drive Alcubierre proposed in the 80's, I think... maybe the 90's. I'm not sure when. A Spanish mathematician or physicist who was a fan of Star Trek.

EDIT: My understanding of physics is pretty minimal. I'm more than happy for someone to correct me and explain what I got wrong. This type of stuff is fascinating.

Re: Magnetoplasma drive could make Mars transit take 39 days?

#15

Post by sandworm101 »

https://www.spaceflightinsider.com/conferences/vasimr-plasma...

http://spacenews.com/vasimr-hoax/

"Zubrin wrote in SpaceNews: “To achieve his much-repeated claim that VASIMR could enable a 39-day one-way transit to Mars, Chang Diaz posits a nuclear reactor system with a power of 200,000 kilowatts and a power-to-mass ratio of 1,000 watts per kilogram. In fact, the largest space nuclear reactor ever built, the Soviet[-era] Topaz, had a power of 10 kilowatts and a power-to-mass ratio of 10 watts per kilogram. There is thus no basis whatsoever for believing in the feasibility of Chang Diaz’s fantasy power system.”

Note the word used by spacenews: Hoax.

Re: Magnetoplasma drive could make Mars transit take 39 days?

#18

Post by snake_plissken »

Some quick math: 32 miles per second (see one of their linked articles, https://www.spaceflightinsider.com/conferences/vasimr-plasma...) is 155,200 miles per hour. Assume you accelerate at 21 MPH, which is about 1 g (100 KPH ~ 60 MPH, 100 KPH / 32.81 KPH/S^2 = 2.85 s, 60 MPH / 2.85 s). So at 1 g It takes you about 228 days to reach cruising speed, 2 g takes 114 days, 3 g 57 days. So I don't think this would not be useful to transport space crews? Still really cool tho.

Re: Magnetoplasma drive could make Mars transit take 39 days?

#19

Post by api »

a_crc wrote: post #11
api wrote: post #4

Earlier quoted context omitted.

How much thin film PV is that? There's no wind and the solar constant is a lot higher in space even further from the sun. Also remember that space is not dark. Unless you are behind something you are always in daylight if you are near a star.

It's a lot of solar panel. A quick search gives us a figure of 220 watts of power per square meter of space based solar panel. This would mean a 200MW solar collector would need to be almost a million square meters in size. For reference that would be a square the length of 155 NYC city blocks on each side.

Hmm... or maybe some smaller panels plus a really enormous and very very thin reflective collector for concentrating solar. Keep in mind that things can be very thin in space.

It would still weigh a lot though, and heat would be a major issue. You wouldn't want to melt the solar panels.

This would require someone much more knowledgable to determine if it's feasible.

Edit: I wonder if you'd get some amount of solar sail effect in addition to the plasma rocket? Of course this would help you one way and hurt you the other way.

Re: Magnetoplasma drive could make Mars transit take 39 days?

#20

Post by codeduck »

a_crc wrote: post #11
api wrote: post #4

Earlier quoted context omitted.

How much thin film PV is that? There's no wind and the solar constant is a lot higher in space even further from the sun. Also remember that space is not dark. Unless you are behind something you are always in daylight if you are near a star.

It's a lot of solar panel. A quick search gives us a figure of 220 watts of power per square meter of space based solar panel. This would mean a 200MW solar collector would need to be almost a million square meters in size. For reference that would be a square the length of 155 NYC city blocks on each side.

A million square metres is one square kilometre. It could be built but it would be heavy. A circular sail with a radius of just over 600 metres would do it.
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